/*
 * acm1629.c
 *
 *  Created on: 28 Mar 2010
 *      Author: xuxu
 */

#include<stdio.h>
int main()
{
	int n;
	int result;
	int i,j;
	while(scanf("%d",&n)!=EOF)
	{
		result=0;
		for(i=1;i<=n;i++)
			result+=i*(i+1)/2;
		for(i=1;i<n;i++)
		{
			for(j=i;j<n;j++)
			{
				if(j+i-1>=n)
					break;
				result+=j-i+1;
			}
		}
		printf("%d\n",result);
	}
	return 0;
}
